Safe As Houses
by MeridianGrimm
Summary: Nagisa gets invited to hang out with Karma after school and discovers the many perils of his friend's home.


**Recap of the prequel, "Demon-shaped":** Yako and Neuro found a half-demon, half-human baby on a case and learned that the kid - Karma - had no family left. Yako decided to raise Karma, since a demon baby wouldn't do well with an adoptive family who was ignorant of demons, and asked Neuro to be her (platonic) co-parent.

What even are timelines anyway. I guess this fic takes place sometime in the middle of Assassination Classroom.

I'm still figuring out how to write Karma and Nagisa's characters, so please let me know how I did! Also, thank you so much to Oort on AO3 for reading through a draft of this :)

* * *

"What are you up to after school today?"

Nagisa shrugged, zipping his backpack closed. "Homework, probably chores."

Karma yawned dramatically. "Boring. Wanna come over to my house instead?" His classmate looked at him and there was a long pause that Karma couldn't quite read. "Well, I guess if you're that set on doing homework…" he prompted.

"No, that's fine. I'd like that. It's just that you've never asked before." Nagisa left a message on his answering machine at home and the two ambled down the mountain at their usual pace, Nagisa chatting with other Class E kids they passed along the way.

As they got on the train, Karma checked his messages. _Something from Mom?_ "Mm, before we go home, I have to stop in to see my folks at work and pick something up. I'll let them know you're staying for dinner too."

"You didn't ask first?"

"Nah, they won't mind."

"What do your parents do? I remember you said that they like India when we were doing the henna tattoos."

"Yeah, my old man goes crazy for them, and they take cases out there at least once a year." Though it wasn't like he didn't use sharpies on Mom for the same effect at home.

"So they do contract work?"

Karma shrugged. "Something like that."

The office wasn't far from the station, part of the reason his parents had picked that location, so the pair reached the office building shortly. Godai exited the building as they approached, flicking out a cigarette pack with noticeable irritation. "Yo, Uncle Godai."

Godai grumbled, "Your dad's in today," which explained the cigarettes – he'd mostly kicked the habit when Karma was in primary school, but he was an easy target for pranks, which led to a lot of stress in his life.

Karma, of course, would _never_ add to that stress. Nope, it was definitely all his adoptive father's fault. Karma would never switch the language settings on Godai's home computer, tinker with his ad block, and sign him up for all sorts of irritating email lists…

Though now Godai was into crochet because of those emails, so the trick had backfired a little. He'd have to do better next time, maybe order fire ants online and have them delivered to Godai's house.

As Karma pushed open the front door, he clarified Godai's comment for Nagisa: "My dad's been splitting his time between work and reorganizing databases at police headquarters." After the nth case where having full, accurate police records online would have solved the case in minutes, Yako had insisted that Neuro do something about it with Evil Script.

They scaled four flights of stairs in silence, and Nagisa noticed that Karma didn't bother knocking when they reached the door with "Katsuragi Yako's Detective Agency" emblazoned in black lettering. Nagisa's eyebrows jumped. There wasn't a single person in Japan who hadn't at least heard of Katsuragi Yako. She'd worked cases across the world for eighteen years. Could Karma's mother be…?

Karma just waltzed in like he owned the place and strode over to one of the desks, behind which sat the detective herself. _It seems a bit small to be the office of such a famous detective,_ Nagisa thought, scanning the space. "Hey, Mom," Karma said, watching with apparently no surprise as the woman scarfed down a pre-made bento in seconds. From the number of empty containers on her desk, it was her seventh. "Got my meds?"

His mother smiled at him and nodded, opening her desk drawer. "Neuro just picked them up. We're doing a case-by-phone for the U.S. about a murdered politician, so I didn't think I'd be home tonight to give them to you myself." She lowered her voice. "You've been out since Tuesday, haven't you?" Nagisa made a point to turn and look interested in the awards on the wall as they continued their private family discussion. Karma _had_ looked a little drained this week and there'd been fewer smartass remarks. He'd also skipped gym class more than usual, though with Karma that may have been for any reason or no reason at all.

"This is Nagisa-kun," Karma announced when they were done, raising his voice to a normal level and gesturing to his friend. "He's coming over tonight to hang out and plan an assassination."

Katsuragi Yako nodded courteously, not even batting an eye at the mention of Class E's secret mission. Nagisa was going to have to ask Karma about that. "Nice to meet you."

"Likewise," he replied, bowing. It wouldn't be polite to ask about the different last names, but there was probably a simple answer. Maybe Karma's mother had kept her unmarried name because "Katsuragi Yako" was recognized worldwide. Nagisa would have considered the possibility of divorce, but from what Karma said, it sounded like his parents got along well.

Nagisa suddenly felt movement behind him and he whirled, hands moving automatically to the knives in his sleeves. They were anti-Korosensei material and therefore useless on humans, but training was training and Nagisa was ready for a fight by the time he came face-to-face with the room's other occupant. He'd heard no steps, no breathing, nothing, just a tickle at the back of his neck. It was a mark of skill that he hadn't noticed the man so far.

The person before him was strikingly tall, and though the man was skinny and not visibly armed, Nagisa got the same feeling from him that he did from Korosensei. This man was powerful in a way that his appearance concealed. Nagisa took slow breaths to calm himself, waiting for the other figure to twitch.

"Akabane-san?" he asked when his voice was steady.

The man grinned, sending a shiver down Nagisa's spine. "Nougami Neuro, but you're correct that Karma is my son."

Nagisa's instincts were still screaming "danger", but he lowered his weapons. "Pleased to meet you."

"We shall see," Neuro replied cryptically, then slithered past to the detective's desk. "Yako, we will need extra cases to make up for the energy spent on the police databases. Do see about that, or I'll need to… _redecorate_ … the office." Karma's mother visibly shuddered.

Karma pocketed the bottle of pills, gave his father a light punch on the arm as both greeting and farewell, and led Nagisa back out.

"So your mom's the famous detective," Nagisa observed once they'd reached the stairwell.

"Yep." Karma waved away the next question before Nagisa could ask. "People always want to meet her, so I don't advertise it." Nagisa nodded in understanding.

"You don't really look like them," he commented, though after meeting Neuro, Nagisa now had a suspicion of where the aptitude for violence came from and why Korosensei didn't faze Karma in the slightest.

"Oh, Mom adopted me," Karma replied casually. That raised more questions, but Nagisa stayed quiet as Karma continued: "And it turns out Neuro's distantly related to my real father. They've been working together since Mom was in high school, though, years before you and I were around."

That still left the question about Karma's last name, since "Akabane" was shared with neither parental figure, but the logical guess was that it had belonged to his deceased relations.

Huh. This was the closest that Karma had ever come to telling someone about his family history. The fact that Neuro and Yako had found him on a case and that Karma's late father had been a demon were secrets for another day, but it looked like Nagisa already had some idea that Neuro wasn't normal. Fantastic instincts, as usual.

Karma stopped by the first floor vending machine to buy a juice box and popped one of the pills made of compressed demonic miasma. By the time he finished the juice box he felt better than he had all week. Miasma deprivation wouldn't kill him, being half human, but the small doses made breathing easier. Karma had speculated that he'd probably need to take oxygen pills if he ever visited Hell.

"So Karma-kun," Nagisa began in a deceptively innocent tone that immediately got Karma's full attention. "What was that about mentioning assassination?"

Karma snorted. "You think I could keep a secret from two world-class detectives who live with me?"

"Yes," he replied instantly, and Karma smiled at the compliment.

It was true – he could've kept the situation with Class E a secret from his parents if he'd wanted, but honestly, he didn't care enough. "Well, it's probably fine," Karma finally said. "Karasuma-sensei and all them were just worried that parents would take their kids out of school or start a media panic."

"You could've gotten in trouble."

"You gonna tell on me?" Karma asked with a lopsided grin and a raised eyebrow. " _Na-gi-sa-kun_?"

Nagisa flushed. "You always say it like that. It's like you're mocking me for having a girly name."

"I mean you're only fifteen, there's still time…" Karma said leadingly.

"Karma-kun," Nagisa warned, clearly trying to imitate Karasuma's stern expression but looking more like a pouting puppy.

Karma couldn't let the subject drop without one last dig. "At least the image of Nagisa-chan is preserved digitally for posterity." Nagisa gave him a light shove. "Alright, I'll stop," he laughed.

"It's a good thing I know you're not serious."

Karma briefly recalled the memory of Nagisa's mother untying her son's hair during the parent-teacher conference and decided to change the subject. "You're probably the first person I've known who _could_ come over my house."

"Why?"

"My old man sets traps."

"What kind of traps?"

"Non-lethal. Well, no one's died _yet_. The bathtub one was a close call with Mom, but that's what CPR is for, right? Your reflexes are pretty good, though, so I reckon you could avoid most of them."

"Oh, Karma."

Karma continued to talk gleefully about the perils of his home, and Nagisa couldn't tell if it was an elaborate joke or he was being serious. Regardless, Nagisa knew he'd be jumpy the whole time he was at the Katsuragi household. Alone with Karma in a house full of traps. What could go wrong?

When they got to his doorstep – the house was ordinary enough, nothing that suggested there were terrors within – Karma dropped his keys and Nagisa twitched at the sound, ready for attack. Was this what it was like to be an assassin's target, never knowing when danger was coming? Being on the other end of this wasn't much fun.

Well, maybe he should think of it as a test. It would show how far his observation skills had progressed since coming to Class E, and maybe he could get some insight into Korosensei's mindset during the assassination attempts against him.

Surprisingly, he felt a little better after that.

They slipped off shoes in the genkan and Nagisa felt the air move just before an arrow came flying out of nowhere. He ducked and the arrow stuck in the door. The poor door looked like it was the victim of many such attacks, as Nagisa could identify dozens of other dents, several colors of faded paint, and food stains.

"Huh, Dad must really be low on energy lately if he's resorted to arrow traps. Want a snack?" Karma dropped his backpack on the floor and strode towards the kitchen.

"I'm not sure I'd trust anything in this house that you'd feed me, Karma-kun."

Karma flashed a mischievous grin. "Probably wise of you. Glass of water? You can get it from the tap."

"Thanks." Nagisa took the cup Karma offered, running his finger around the rim and discreetly sniffing for anything unusual while Karma filled up his own glass. The tap did seem to be dispensing water, rather than a mystery liquid, so he followed suit and trailed after Karma up the stairs.

Nagisa quickly realized why Karma took them two at a time when one of the steps collapsed under his foot. He managed to catch himself before knocking his head on another stair, but his glass spilled everywhere. Strangely, though, when he crawled up a step and turned around, the stairs below looked normal.

Karma poked his head back around the corner. "That was one of mine."

Nagisa examined the previous step more closely. Nothing seemed to be wrong with it. "Did you cut it in half and rig some kind of spring underneath it?"

Karma just smiled enigmatically.

Like everything else, Nagisa seemed to quickly recover from the novelty of being in a house full of tricks. He didn't comment on the sticky substance that coated the ceiling of Karma's room, though Karma saw him scrutinize it for several long seconds. "I expected your room to be a little less neat," was his only remark.

They did brainstorm assassination tactics for a while, and the paper spread out on the floor was covered in shorthand and doodles by the time Karma got bored. "Video games?" he suggested when they were done.

"Sure."

After settling in on the couch downstairs, Karma took the controller with the "A" button that let off electric sparks and handed Nagisa the one with the metal spike sticking out of the joystick. Though they were both impaired, Karma and Nagisa nevertheless enjoyed racking up a new high score as a team on Karma's favorite racing game. Nagisa still seemed suspicious of the food when they decided to pause for dinner, so Karma ordered a pizza for the two of them and they watched part of an action film that was on TV.

At the end of the night, Nagisa slipped on his shoes and side-stepped another zooming arrow like it was nothing. Karma bit back a smile, pleased that his confidence in Nagisa had not been misplaced. Perhaps Karma didn't have to wait until he moved out to have people over.

The next morning, as Karma settled into his seat a few minutes before Korosensei was due to show up, he heard a small _twang_ from above and immediately leapt out of his seat. After all, he hadn't survived Neuro's idea of fun without developing quick reactions. A split second after he moved, a balloon filled with water landed on his desk and splattered everywhere.

All of Karma's classmates whipped around and stared. "Is someone trying to bully _Karma?"_

Karma leaned in to see that the balloon's knot still had clear, thin fishing line tied around it, and he followed the line up to see it disappear in between the ceiling tiles. Since the tiles could be pushed up, the fishing line had probably been strung through the space above them, threaded between two more tiles, and then held by the culprit. It would be impossible to tell who had set this up, though, since the other end would have disappeared into the ceiling as the balloon fell.

"Did he do something to Korosensei? Is this revenge?"

"Nah, Korosensei wouldn't have retaliated like that. He grooms people." The murmurings continued, but Karma ignored them to zero in on Nagisa. The boy blinked, expressing the same amount of surprise as their other classmates before turning back to the front, but the execution was a little too perfect.

Karma strolled up and plopped into the empty chair in front of his friend. "Are you sure you want to start this with me, Nagisa-kun? I've had fifteen years of practice, and I'm _very_ creative."

Nagisa remained unfazed, propping his head on his hand with measured nonchalance. "Fifteen years of being pranked by same person and you start to pick out their habits. Sure, the tricks have probably evolved over time, but if it becomes normal then you're not really being challenged anymore. Throw a new person into the mix and suddenly you're forced to think outside the box again."

"You just want to get back at me for the stair prank, don't you?"

Nagisa abandoned the pretense and laughed. "You got me. But making you a better assassin wouldn't hurt. Everyone needs to be at the top of their game if we're going to take out Korosensei."

"It's on, then."

* * *

Alternate title: Home is Where the Hazards Are

Come talk to me on my tumblr (meridiangrimm) about Assassination Classroom and Majin Tantei Nougami Neuro.


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